DESCRIPTION: The overall goal of this laboratory is to understand the circuitry of the cerebral cortex and how it is related to perception and behavior. Central to this goal is the study of functional architecture, which deals with the way that information represented by the firing patterns of single neurons is anatomically organized into computational structures such as columns and maps. Knowledge of the functional architecture is crucial to an understanding of how the brain works for two major reasons. 1) When combined with knowledge of intrinsic and extrinsic anatomical connections of a cortical area, it yields insights into the nature of the cortical circuitry, how it performs its computations and how it may develop. 2) When combined with behavioral and microstimulation techniques, it can be used to demonstrate causal connections between neural activity and behavior. Understanding these-- relationships is the central goal of neurobiology and a necessary first step in understanding and treating diseases of the brain. An extrastriate visual motion processing area, the middle temporal visual area (area MT), is an excellent place to pursue the issues outlined above. A great deal of information has already been accumulated on the stimulus-response properties of its neurons and its basic connections with other brain areas. Lesion studies and microstimulation experiments have indicated a prominent role in several visual behaviors such as discrimination of direction of motion and visual tracking. The missing element has been an understanding of the functional architecture, which can be used to fit together the many pieces of the puzzle and provide a firm foundation for its relationship to behavior. It will be the goal of this proposal to elucidate the functional architecture of area MT by relating single neuron response properties to the anatomical structure of area MT and then to use microstimulation as a probe to assess the behavioral significance of the functional architecture. SUMMARY: In this well-written and detailed application, Dr. Born requests five years of funding for a comprehensive study of the modular organization of area MT in the macaque monkey. From his preliminary data and previous publications, Dr. Born presents strong evidence that MT is divided up into at least 2 different kinds of columns which he calls bands and interbands. The principal investigator has strong evidence that these bands contain 2 very different kinds of neurons that subserve very different motion tasks: self motion and object motion. In a comprehensive and wide ranging series of experiments he proposes to study the physiology, projection, functional architecture and behavioral function of these cells. The experiments are well designed, and address a critical aspect of this much studied higher cortical area. Given the ample preliminary data there is a high probability of success.